Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 70

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Observe Safety Guidelines detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
The machine output is intermittently
lost. Gas flow and high frequency
are also interrupted.
The arc "flutters" when TIG welding. 1. The tungsten electrode may be
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely,
contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed.
Call 1-888-935-3877.
TROUBLESHOOTING AND REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
TIG MODE PROBLEMS
1. The problem may be caused by
high frequency
Make sure that the machine is
grounded properly according to
the installation instructions.
there are other high frequency
sources in the area, make certain
they are grounded properly.
2. Check the Arc Start switch or
Amptrol for proper operation and
loose connections.
too large in diameter.
2. The tungsten electrode may
needed sharpening.
3. If helium shielding gas is used,
reduce the percentage of helium.
4. Adjust the gas flow rate to the
proper level for the process being
used.
5. Check gas hoses and connec-
tions for leaks.
CAUTION
SQUARE WAVE TIG 355
RECOMMENDED
COURSE OF ACTION
1. The machine internal ground
interference. connections may be loose.
Check the mounting screws on
the protection
If bypass boards, and the feed-
thru board.
2. The protection
boards may be faulty. Check or
replace.
3. Perform the Arc Start Trigger
Circuit Test.
1. Check for loose shunt connec-
tions, leads #222 and #221.
See Wiring Diagram.
2. Check polarity switch for loose
or faulty connections.
3. Perform the Static & Active
SCR Bridge Tests.
4. Check components R6 and C6
in the high voltage transformer
primary circuit. Replace if nec-
essary.
5. The control board may be faulty.
Replace.
6. The power board may be faulty.
Replace.
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board, the
or bypass